1. Field of the Invention
The present invention relates to a vibration motor.
2. Description of the Related Art
Brushless vibration motors in the shape of a thin coin are typically used as silent notification devices in mobile communication apparatuses or the like, or for other purposes. JP-A 2009-130969 describes such a vibration motor, in which a plurality of flat air-core coils 42 to 45 are arranged around a spindle 30.
When the vibration motor described in JP-A 2009-130969 is to be reduced in radial dimension, it is necessary to reduce the radial dimension of each of the flat air-core coils 42 to 45. A radially extending portion of each of the flat air-core coils 42 to 45 defines a torque generating portion that causes a torque to be generated between an annular magnet 50 and the flat air-core coils 42 to 45. Therefore, a reduction in the radial dimension of each of the flat air-core coils 42 to 45 leads to a reduction in the torque and a reduction in vibrations of the vibration motor. It is also conceivable to shift each of the flat air-core coils 42 to 45 radially inward to reduce the radial dimension of the vibration motor. However, a washer 20 is fixed to the spindle 30 at a position radially opposed to each of the flat air-core coils 42 to 45, and it is therefore difficult to shift each of the flat air-core coils 42 to 45 radially inward to a large degree.